a = input().split()
try:
    prost = [101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151,  157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229 ,233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997]
    b = {"nine": 9, "eight": 8, "seven": 7, "six": 6, "five": 5, "four": 4, "three": 3, "two": 2, "one": 1, "zero": 0}
    prnumb = b[a[0]] * 100 + b[a[1]] * 10 + b[a[2]]
    for i in range(len(prost)):
        if prost[i] > prnumb:
            b = prost[i] - prnumb
            m = prnumb - prost[i - 1]
            if b < m:
                print(prost[i])
            else:
                print(prost[i - 1])
            break
    print(997)
except:
    print("Wrong input")